Vasovagal syncope (VVS) is a condition marked by a sudden drop in blood pressure resulting in fainting. It is not only unpleasant for the patient, but also potentially dangerous, as fainting may lead to injuries from falls. Some patients are at risk of recurrent episodes of VVS, and for them, VVS may present a serious impediment to daily activities and enjoyment of life.
Therapy to counteract VVS may include delivery of a drug to address the VVS. In patients having an implanted cardiac pacemaker, therapy may include pacing the heart to increase the heart rate and thereby increase the cardiac output to compensate for a drop in blood pressure. These techniques are generally more effective when applied well before the onset of an episode of VVS. If the therapies are not applied well before the onset of VVS, the therapies may not be effective in preventing the patient from fainting. The onset of the fainting spell may be marked by a sudden drop in heart rate or blood pressure, but by the time a drop in heart rate or blood pressure is detected, it is often too late to prevent the fainting spell.